fun main() {
    //将每个元素值乘以3以后累加起来
    //folder
    val foldedValue = listOf(1, 2, 3, 5).fold(2) { acumulator, number ->
        println("acumulator value:$acumulator")
        acumulator + (number * 3)
    }
    println("final value:$foldedValue")
}